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/*
Copyright (C) 2020 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "ca_poly.h"
void
_ca_poly_evaluate_horner(ca_t y, ca_srcptr f, slong len,
const ca_t x, ca_ctx_t ctx)
{
if (len == 0)
{
ca_zero(y, ctx);
}
else if (len == 1 || ca_check_is_zero(x, ctx) == T_TRUE)
{
ca_set(y, f, ctx);
}
else if (len == 2)
{
ca_mul(y, x, f + 1, ctx);
ca_add(y, y, f + 0, ctx);
}
else
{
slong i = len - 1;
ca_t t, u;
ca_init(t, ctx);
ca_init(u, ctx);
ca_set(u, f + i, ctx);
for (i = len - 2; i >= 0; i--)
{
ca_mul(t, u, x, ctx);
ca_add(u, f + i, t, ctx);
}
ca_swap(y, u, ctx);
ca_clear(t, ctx);
ca_clear(u, ctx);
}
}
void
ca_poly_evaluate_horner(ca_t res, const ca_poly_t f, const ca_t a, ca_ctx_t ctx)
{
_ca_poly_evaluate_horner(res, f->coeffs, f->length, a, ctx);
}